Design,Simulation And Fabrication Of Silica Based Arrayed Waveguide Grating

Based on the fundamental theories of planar lightwave circuits and the basic principle of an arrayed waveguide grating (AWG), some simulation methods used for estimating the performance of an AWG and some improved design methods for optimizing the performance of an AWG are studied in detail in this thesis. Experimental studies of the fabrication of an AWG are also carried out.Simulation of an AWG is very important for the optimal design of an AWG. The effective index method is applied to simplify an AWG structure from 3D to 2D. Two simulation methods are presented in detail based on the Gaussian beam propagation formula and the finite difference beam propagation method. The first one is an analytical method which is simple and fast. The second one is a numerical method which gives more accurate results and can be used for simulation of a complicate AWG with e.g. a MMI section to flatten the spectral response.In this thesis, a multiple-stigmatic-point method (MSPM) is applied to improve the conventional Rowland-type design, which is especially important for designing an AWG when the total number of the channels is large. It greatly improves the performance of an AWG, such as the channel uniformity, the crosstalk and the insertion loss.A method used for flattening the spectral response of an AWG is presented based on the MSPM. This simple and straightforward method is used to design multiple sub gratings to obtain a flattened spectral response with a high uniformity of all channels.A method used for designing a flat-field AWG is also presented based on the MSPM. In this design, the images of all the channels are on the same line. This greatly simplifies the structure of an AWG and makes it much easier to integrate with other devices.These three methods are all based on the MSPM, and thus can be combined to obtain simultaneously large channel number flatten spectral response and flat-field AWG.Experimental studies of the fabrication of the 8-channel 16-channel AWG with 200GHz channel spacing are carried out. PECVD ICP and lift-off technology are used for fabricating Si-based SiO2 AWG demultiplexers. Samples of the fabricated AWG are tested and the experimental results are obtained.